Solution for chemical rectifiers



Sept. 150,-` 929. F. T. Bowman-VCH SOLUTION FOR CHEMICAL RECTIFIERS Filed June 2l, 1924 :iov 30% of the mixed salts are preferable, and my best results have been obtained with con-` Patented Sept. 10, 1929.

UNITED y STATES PATENT ol-llcifzp` `'l'BIEIJ '.1.V BOWDITCH, O ELNIHURST, NEW'YORK, ASSIGNR T0 NATIONAL CARBON l COMPANY, INC., A CORPORATION F.NEW YORKJ` SQLUTION FOR CHEMICAL BECTIFIERS.

Alipneation mea June g1, 1924. serial No. 721,54'5.

The invention relates to the rectification of alternating currents by means of appara- 'aqueous solution of an ammonium phosphate, such as diammonium hydrogen phosphate, land an ammonium citrate, such as the normal salt, preferably containing also a small-quantity ofa readily ionizable compound, such as potassium citrate, to increase the conductivity; Ammonium phos-` phate and citrate are both well-known lmforming agents for `rectifier solutions, but I have found that remarkable improvement can beeiected by using both the saltsin certain proportions in the same solution.

It is a primary object'of the present invention to construct a rectiier of minimum volume, which will have a tlong service life and desirable operatingI characteristics; I have found -that very concentrated solutions of citrate and phosphate must be used to obtain long'service from a small volu-Ineof solution. Solutions containing not less than centrations of about Stated in terms ofthe citrate and phosphate radicles, the rectifier solution should contain' not less than 20% of the mixed radicles, and preferably about 38%J I have also'foundthat service life is dependent to a surprising idegree upon the re; lation between the quantitites of the salts or their acid radiclesiin solution.

The attached drawing is a curve which `shows the effect of varying the relative quantities of` citrate vand phosphate. Ordin nates n the curve represent total ampere hours of direct current delivered up to the time of failure bya rectifier containing 300 c. c. bf solution, while absciss are the perlcelitages ofI ammonium` phosphate 'in the` mixture of fsalts., TheI total quantity of mixed salts is constant in the test illus- .trated by the curve, and vis equal to the weight of Water in the rectifying solution.

'The solution contains about 0.3% of potassium citrate to increase -its conductivity.

It will be observed that when the proj portion fof phosphate in the salt mixture is small, the service life increases very ra idly with increase in the ammonium phospliate; that the life reaches a maximum when the percentage of"phosphate is about 15; and that increasing-the phosphate beyond 25% reduces the -lite rapidly, a mixture of equal Weights of the two salts giving but -little more than 20% of the life of the'optimum 65 mixture. p ,A

The effect of proportions vof the salts on life...is so great when the phosphate is less than 10% of the mixture that I am unable to specify the exact point `Vwhere the s* curve begins noticeably to Hatten, but it may be safely said that not more than difteen times as much citrate as lphosphate shouldbe used for the best results. The quantity of'citrate should be at least three times as great as the quantity of phosphate. ,The-ratio of citrate' radicle (36H507 to phosphate radicle P04 in solutions giving the longest service will also fall between 3 and' 15.

The service life of a rectifier containing a solution such as those described abovecan also b'e increased'by substituting citric acid for ammoniumsctrate. The maximum service life plotted ,on the curve of the drawing is about 190 ampere hours. QA solution 85 identical with that which gave this life with the exception that one-half the ammoniuln citrate was replaced by ya quantity of citri-c acid carrying an equal number of thecitrate radicles, gave 206 ampere hours. By 90.

replacing all the ammonium citrate of the vcurrents pass through the rectifier, as dur-V ing theointerval before the rectifying film has formed, the rectifier may heat up soL much that the water-Wilbe boiled out of it,

destroying the rectifier. Whether ammonium citrate, citric acid, or a mixture of the two is to be used depends therefore upon the manner in which the rectifier is to be emIployed.

- claim:

1. A rectifier solution containing citrate and phosphate radiales, the ratio of citrate radiale to phosphate radiale falling between 3 and 15.

2. A rectifier solution containing more than 20% of citrate and phosphate radiales,

vthe ratio of citrate radiale to phosphate radiale falling between 3 and 15.

3. A rectifier solution containing more than 20% of citrate and phosphate radiales, the ratio of citrate radiale to phosphate radiale falling between 3 and 15; the solution containing also an alkali metal compound.

4. A rectifier .solution containing ammonium citrate and ammonium phosphate, the ratio of the citrate to the phosphate falling between 3 and 15 and the two salts together being at least 30% of the solution.

5. `A rectifier solution containing about 33% of citrate radiale and about 7.5% of ammonium, phosphate.

6. A rectifier solution containing about 42.5% of ammonium citrate and about 7 .5%

5 of ammonium phosphate.

In testimony whereof, I aiix my signature.

FRED T. BOWDITCH. 

